This invention relates generally to methods and apparatus for attaching soft tissue to bone, and more particularly to anchors and methods for securing connective tissue, such as ligaments or tendons, to bone. The invention has particular application to arthroscopic surgical techniques for reattaching the rotator cuff to the humeral head, in order to repair the rotator cuff.
It is an increasingly common problem for tendons and other soft, connective tissues to tear or to detach from associated bone. One such type of tear or detachment is a xe2x80x9crotator cuffxe2x80x9d tear, wherein the supraspinatus tendon separates from the humerus, causing pain and loss of ability to elevate and externally rotate the arm. Complete separation can occur if the shoulder is subjected to gross trauma, but typically, the tear begins as a small lesion, especially in older patients.
To repair a torn rotator cuff, the typical course today is to do so surgically, through a large incision. This approach is presently taken in almost 99% of rotator cuff repair cases. There are two types of open surgical approaches for repair of the rotator cuff, one known as the xe2x80x9cclassic openxe2x80x9d and the other as the xe2x80x9cmini-openxe2x80x9d. The classic open approach requires a large incision and complete detachment of the deltoid muscle from the acromion to facilitate exposure. The cuff is debrided to ensure suture attachment to viable tissue and to create a reasonable edge approximation. In addition, the humeral head is abraded or notched at the proposed soft tissue to bone reattachment point, as healing is enhanced on a raw bone surface. A series of small diameter holes, referred to as xe2x80x9ctransosseous tunnelsxe2x80x9d, are xe2x80x9cpunchedxe2x80x9d through the bone laterally from the abraded or notched surface to a point on the outside surface of the greater tuberosity, commonly a distance of 2 to 3 cm. Finally, the cuff is sutured and secured to the bone by pulling the suture ends through the transosseous tunnels and tying them together using the bone between two successive tunnels as a bridge, after which the deltoid muscle must be surgically reattached to the acromion. Because of this maneuver, the deltoid requires postoperative protection, thus retarding rehabilitation and possibly resulting in residual weakness. Complete rehabilitation takes approximately 9 to 12 months.
The mini-open technique, which represents the current growing trend and the majority of all surgical repair procedures, differs from the classic approach by gaining access through a smaller incision and splitting rather than detaching the deltoid. Additionally, this procedure is typically performed in conjunction with arthroscopic acromial decompression. Once the deltoid is split, it is retracted to expose the rotator cuff tear. As before, the cuff is debrided, the humeral head is abraded, and the so-called xe2x80x9ctransosseous tunnelsxe2x80x9d, are xe2x80x9cpunchedxe2x80x9d through the bone or suture anchors are inserted. Following the suturing of the rotator cuff to the humeral head, the split deltoid is surgically repaired.
Although the above described surgical techniques are the current standard of care for rotator cuff repair, they are associated with a great deal of patient discomfort and a lengthy recovery time, ranging from at least four months to one year or more. It is the above described manipulation of the deltoid muscle together with the large skin incision that causes the majority of patient discomfort and an increased recovery time.
Less invasive arthroscopic techniques are beginning to be developed in an effort to address the shortcomings of open surgical repair. Working through small trocar portals that minimize disruption of the deltoid muscle, a few surgeons have been able to reattach the rotator cuff using various bone anchor and suture configurations. The rotator cuff is sutured intracorporeally and an anchor is driven into bone at a location appropriate for repair. Rather than thread the suture through transosseous tunnels which are difficult or impossible to create arthroscopically using current techniques, the repair is completed by tying the cuff down against bone using the anchor and suture. Early results of less invasive techniques are encouraging, with a substantial reduction in both patient recovery time and discomfort.
Unfortunately, the skill level required to facilitate an entirely arthroscopic repair of the rotator cuff is inordinately high. Intracorporeal suturing is clumsy and time consuming, and only the simplest stitch patterns can be utilized. Extracorporeal knot tying is somewhat less difficult, but the tightness of the knots is difficult to judge, and the tension cannot later be adjusted. Also, because of the use of bone anchors to provide a suture fixation point in the bone, the knots that secure the soft tissues to the anchor by necessity leave the knot bundle on top of the soft tissues. In the case of rotator cuff repair, this means that the knot bundle is left in the shoulder capsule where it is able to be felt by the patient postoperatively when the patient exercises the shoulder joint. So, knots tied arthroscopically are difficult to achieve, impossible to adjust, and are located in less than optimal areas of the shoulder. Suture tension is also impossible to measure and adjust once the knot has been fixed. Consequently, because of the technical difficulty of the procedure, presently less than 1% of all rotator cuff procedures are of the arthroscopic type, and are considered investigational in nature.
Another significant difficulty with current arthroscopic rotator cuff repair techniques are shortcomings related to currently available suture anchors. Suture eyelets in bone anchors available today, which like the eye of a needle are threaded with the thread or suture, are small in radius, and can cause the suture to fail at the eyelet when the anchor is placed under high tensile loads.
There are various bone anchor designs available for use by an orthopedic surgeon for attachment of soft tissues to bone. The basic commonality between the designs is that they create an attachment point in the bone for a suture that may then be passed through the soft tissues and tied, thereby immobilizing the soft tissue. This attachment point may be accomplished by different means. Screws are known for creating such attachments, but suffer from a number of disadvantages, including their tendency to loosen over time, requiring a second procedure to later remove them, and their requirement for a relatively flat attachment geometry.
Another approach is to utilize the difference in density in the cortical bone (the tough, dense outer layer of bone) and the cancellous bone (the less dense, airy and somewhat vascular interior of the bone). There is a clear demarcation between the cortical bone and cancellous bone, where the cortical bone presents a kind of hard shell over the less dense cancellous bone. The aspect ratio of the anchor is such that it typically has a longer axis and a shorter axis and usually is pre-threaded with a suture. These designs use a hole in the cortical bone through which an anchor is inserted. The hole is drilled such that the shorter axis of the anchor will fit through the diameter of the hole, with the longer axis of the anchor being parallel to the axis of the drilled hole. After deployment in to the cancellous bone, the anchor is rotated 90xc2x0 so that the long axis is aligned perpendicularly to the axis of the hole. The suture is pulled, and the anchor is seated up against the inside surface of the cortical layer of bone. Due to the mismatch in the dimensions of the long axis of the anchor and the hole diameter, the anchor cannot be retracted proximally from the hole, thus providing resistance to pull-out. These anchors still suffer from the aforementioned problem of eyelet design that stresses the sutures.
Still other prior art approaches have attempted to use a xe2x80x9cpop rivetxe2x80x9d approach. This type of design requires a hole in the cortical bone into which a split shaft is inserted. The split shaft is hollow, and has a tapered plug leading into its inner lumen. The tapered plug is extended out through the top of the shaft, and when the plug is retracted into the inner lumen, the tapered portion causes the split shaft to be flared outwardly, ostensibly locking the device into the bone.
Other methods of securing soft tissue to bone are known in the prior art, but are not presently considered to be feasible for shoulder repair procedures, because of physicians"" reluctance to leave anything but a suture in the capsule area of the shoulder. The reason for this is that staples, tacks, and the like could possibly fall out and cause injury during movement. As a result of this constraint, the attachment point often must be located at a less than ideal position. Also, the tacks or staples require a substantial hole in the soft tissue, and make it difficult for the surgeon to precisely locate the soft tissue relative to the bone.
An approach that also utilizes the difference in density between the cortical and cancellous layers of bone is described in U.S. Pat. No. 5,618,314 to Harwin, et al. In that design, the anchor device uses stationary wing members which extend proximally and radially outward from the anchor member and which employ a cutting means along the wing members. In this approach, the anchor device is inserted into a hole which has been drilled into the bone and then rotated radially such that the wing members with the cutting means are disposed into the cancellous layer of bone just below the cortical bone. With this device, a relatively small surface area of the wing members are disposed against the cortical bone in comparison with the present invention, making it more prone to being pulled out of the bone structure as proximal tension is applied to the suture.
A number of other various methods of anchoring a suture to bone utilizing the difference in density between the cortical and cancellous bone are described in U.S. Pat. No. 5,417,691 to Hayhurst. One such method describes an anchor with a series of proximally pointing barbs along its member, which is inserted, into a hole in the bone structure, utilizing the barbs as a means of anchoring the device to the bone. This method presents the same disadvantage with respect to the amount of surface area in contact with the bone as described in connection with the Harwin, et. al. patent, supra.
The Hayhurst patent further describes an approach to anchoring a suture to bone using an elongated anchor member shaped to normally assume a straight configuration which is then bent or flexed to allow it to be inserted through a needle or lumen and then expelled such that it returns to its straight configuration in a position generally perpendicular to the suture. This approach is designed for applications in which the anchor member may be placed between cartilage and bone and is impractical for use where the suture must be anchored directly to the bonexe2x80x94the applications for which the present invention is specifically designed.
Other similar approaches are described in U.S. Pat. No. 5,417,712 to Whittaker, et al. This patent describes anchor devices using various different barbs and wings to secure the anchor members to the bone. This approach, however, suffers the disadvantage of a small surface area disposed against the bone and a relatively weak construction and resultant anchoring interface.
Bone anchor designs utilizing a means of disposing an anchoring device below the cortical bone in a generally parallel position to the cortical bone and in a perpendicular position to the suture are described in U.S. Pat. No. 5,941,900 to Bonutti and in U.S. Pat. No. 6,045,574 to Thal. These designs use a hole in the cortical bone through which an anchor is inserted. The hole is drilled such that the shorter axis of the anchor will fit through the diameter of the hole, with the longer axis of the anchor being parallel to the axis of the drilled hole. After deployment in to the cancellous bone, the anchor is rotated 90xc2x0 so that the long axis is aligned perpendicularly to the axis of the hole. The suture is pulled, and the anchor is seated up against the inside surface of the cortical layer of bone. Due to the mismatch in the dimensions of the long axis of the anchor and the hole diameter, the anchor cannot be retracted proximally from the hole, thus providing resistance to pull-out.
These anchors, however, do not have the ability to be bent or flexed for deployment through a narrow lumen or hypotube, making insertion and placement difficult. They also suffer from the same disadvantage of a small surface area to be disposed against the cortical bone as the other applications described above.
U.S. Pat. No. 6,146,406 to Shluzas et al. discloses a bone anchor having first and second anchoring legs and a bridge joining the anchoring legs between their proximal and distal ends. Portions of the anchoring legs on a proximal side of the bridge are configured to elastically compress together in response to an insertion force applied to the bone anchor during insertion of the bone anchor into a bone hole, and to plastically splay apart in response to a withdrawal force applied to the bone anchor, which force is applied by pulling on the suture extending proximally from the surgical site. This anchor also has a relatively limited surface area contact with the lower surface of the cortical bone and with the surrounding cancellous bone, and can be difficult and tricky to insert and deploy.
What is needed, therefore, is a new approach for repairing the rotator cuff or fixing other soft tissues to bone, wherein the suture resides completely below the cortical bone surface, there is no requirement for the surgeon to tie a knot to attach the suture to the bone anchor, and wherein the procedure associated with the new approach is better for the patient, saves time, is uncomplicated to use, and easily taught to practitioners having skill in the art.
The present invention overcomes the disadvantages of prior art devices and provides further advantages by utilizing the difference in density in the cortical bone (the tough, dense outer layer of bone) and the cancellous bone (the less dense, airy and somewhat vascular interior of the bone). There is a clear demarcation between the cortical bone and cancellous bone, where the cortical bone presents a kind of hard shell over the less dense cancellous bone.
A major aspect of the present invention is to provide a means to either attach a suture securing device to the inventive anchoring device, or to attach a suture directly to the inventive device outside the body, then deploy the entire apparatus into the procedural area through a lumen in a tube. Once inserted into the procedural area within the bone, the device is expanded to anchor it beneath the cortical layer of bone. When the device is deployed, it extends radially into the cancellous bone just beneath the cortical layer of bone at the point at which the cortical and cancellous layers of bone meet. The manner in which the present invention is designed prevents it from returning, after it has been deployed, to the folded or bent profile it assumed as it was being deployed. This design, moreover, prevents the invention from moving proximally due to the density of the cortical bone against which it is seated, or from moving either distally or radially due to the amount of anchor surface area which is extended into the cancellous bone. This approach is practicable for use in an arthroscopic procedure and eliminates the disadvantages associated with the use of screws, tacks, and staples described above. The present invention solves the problems outlined above by providing innovative bone anchor and connective techniques which permit a suture attachment which lies beneath the cortical bone surface, without the necessity of tying knots.
More particularly, there is provided in a preferred embodiment a bone anchor device for attaching connective tissue to bone, which comprises disk adapted for insertion into a portion of bone. The disk is movable between a bent orientation for presenting a smaller cross-section and an expanded orientation for presenting a larger cross-section, and the disk is substantially planar when in the expanded orientation. The bent orientation is utilized for inserting the disk through a small hole into a region of cancellous bone beneath the cortical bone layer, after which the disk is actuated to move into its expanded orientation so that it will be permanently anchored in the cancellous bone, as it will be too large to return proximally through the hole in the cortical bone layer. The disk is generally elliptical when in the expanded orientation, and presents a generally circular footprint when in the bent orientation and viewed from a proximal position.
In one preferred embodiment, the substantially planar disk is annular, comprising an annular sidewall and a center aperture. Such an embodiment is particularly useful with a separate suture retaining anchor disposed distally of the disk. Two axial suture receiving grooves disposed on an inner surface of the annular sidewall, spaced from one another by approximately 180 degrees, are preferably employed.
In another embodiment, wherein the disk itself may be utilized as the suture retaining anchor, the substantially planar disk is substantially solid, having two small apertures adjacent to one another in a center portion thereof for receiving suturing material therethrough.
A slit is preferably disposed in the disk for facilitating the movement of the disk between the bent orientation and the expanded orientation, and, more preferably, two such slits, spaced approximately 180 degrees apart, are employed. The disk has a longitudinal axis extending between a proximal end and a distal end thereof, wherein the disk bends about an axis which lies transversely to the longitudinal axis. The disk forms a generally xe2x80x9cVxe2x80x9d shape in the bent orientation. In a preferred embodiment, each slit comprises an axial portion extending from the distal end of the disk, and a circumferential portion extending about a portion of an outer sidewall of the disk, wherein the circumferential portion is in communication with the axial portion so that the two slit portions together form each generally xe2x80x9cTxe2x80x9d shaped slit. A thin axial length of the sidewall extends between the proximal end of the disk and the circumferential slit portion. The disk bends about the transverse axis in a region including the thin axial length of each of the two slits. In one embodiment, wherein the disk is formed of flat stock resilient material, such as spring steel, tension applied to opposing edges of the disk cause the bending to occur, because the natural orientation of the disk is its expanded planar configuration. In another embodiment, however, wherein the disk is formed from tubular stock, which is a non-resilient material, such as stainless steel, an axial compressive force applied to the disk causes the bending to occur. In this configuration, the natural orientation of the disk is its bent, reduced configuration, and the axial compressive force is applied to force the disk to its expanded flat configuration.
In preferred embodiments, the disk has a thickness of approximately 0.031 inches and the thin axial length of the sidewall is approximately 0.006 inches long. As noted supra, in one embodiment, it comprises spring stainless steel, and is biased by the spring stainless steel to assume the expanded orientation unless otherwise constrained. In a second embodiment it comprises ordinary stainless steel or other suitable biocompatible material, and must be forced into the expanded orientation.
In another embodiment, designed to substantially increase the pull-out strength of the anchor, a plurality of the aforementioned disks, arranged in a stacked array, are employed.
In another aspect of the invention, there is provided a bone anchor apparatus, which comprises a first tube, a second tube coaxially and slidably disposed within the first tube, and a disk which is movable between a bent orientation for presenting a smaller cross-section and an expanded orientation for presenting a larger cross-section. During deployment of the bone anchor, the disk is disposed within the first tube distally of the second tube, in the aforementioned bent orientation, with a distal end of the second tube engaging the disk. In the spring steel embodiment, tension applied to opposing edges of the disk by an inner wall of the first tube cause the bending to occur. In a preferred embodiment, the first tube comprises a proximal end portion having a first diameter and a distal end portion having a second diameter which is reduced relative to the first diameter. An axial length of the distal end portion is approximately equal to a thickness of cortical bone in a portion of bone into which the disk is to be disposed to function as a bone anchor, wherein a transition region on the tube between the proximal and distal end portions is adapted to function as a stop when the first tube is inserted into a hole in the bone portion, thereby ensuring that a distal end of the first tube is disposed in cancellous bone beneath the cortical bone thickness.
Preferably, there is disposed a slit in an outer wall of the first tube, which slit extends proximally from the distal end of the first tube proximally of the transition region. Additionally, there is a slit in an outer wall of the second tube, wherein the first and second tubes are rotationally oriented relative to one another, when the second tube is disposed within the first tube, so that the slits in each of the first and second tubes are substantially coincident with one another.
In still another aspect of the invention, there is provided a bone anchor apparatus which comprises an anchor body having a first displaceable portion and a second displaceable portion, together with a connecting portion which joins the first and second displaceable portions. Advantageously, the first and second displaceable portions are each moveable from a first orientation wherein portions of each of the first and second displaceable portions are disposed proximally of the connecting portion, and a second orientation wherein the first and second displaceable portions and the connecting portion all lie in substantially the same plane. Preferably, the first and second displaceable portions in combination with the connecting portion comprise a disk, and a suture receiving groove is disposed in each of the first and second displaceable portions. In a presently preferred embodiment, the anchor body is initially disposed in the first orientation.
In yet another aspect of the invention, there is disclosed a method for securing connective tissue to bone. The inventive method comprises steps of securing a first end of a length of suture to a portion of soft tissue to be attached to a portion of bone, and threading a second end of the length of suture through an aperture in a body of a bone anchor disk. The bone anchor disk is disposed within a lumen of a tube, with the disk being disposed in a bent orientation having a reduced cross-section. A distal end of the tube is inserted into a hole within the portion of bone. The disk is then deployed from the distal end of the tube. Once deployed, the disk moves to an expanded orientation, so that the disk becomes anchored within the portion of bone.
In still another aspect of the invention, there is disclosed a method of fabricating a bone anchor device. The inventive method comprises steps of providing a tube of biocompatible material, forming a bone anchor device by making a series of cuts on a first end of the tube, and separating the bone anchor device from a remaining portion of the tube by making a further cut through the tube.